West System Vs. Bondo

[cornbread]

I am working on 2 projects one is making a 9/4 walnut slab into a live edge desk that has a huge knot to fill. So large I considered leaving it (approx 1.5"× 12"×2.25 deep), but some of the wood was rotten, so I got the soft pieces out and decided to fill with epoxy. This is my first attempt at epoxy filling. I purchased a quart/pint of west system 105/206 and it didn't go near as far as I "wood" have hoped. Couple that with project #2 which is an old 5 panel heart pine door that I'm trying to match up for finishing and building a headboard frame, bed rails, footboard. Note, I was lucky enough to find some 5/4 heart pine old growth locally.

So back to my problem, West system is expensive. What other epoxy system could I also try? The only thing I could find on the bondo fiberglass resin, is that it's not as good for boat hulls, but since this is a desk, maybe okay??? Could I apply it over my half filled hole of west system epoxy? Price appears to be about 1/2.

 

[danmart77]

Can you post a photo or two?

 

[Jim M.]

Unless you're going to do a compatibility test, I'd stick with the West System. Or leave it as is, you can always keep M&M in it.

 

[smallboat]

I'm sure there will be other answers but here's my quick take-
A Qt of anything will be 57.75 cu in. The gap you are trying to fill is around 40 cu in if the dimensions you give are close to correct.
So a qt of resin plus the hardener should be plenty to do the job unless something else is going on.
Did it leak out the other side?

WEST is designed to saturate the wood so some will go into the wood fibers, that's why they recommend applying it until it stops soaking in as a first step.

The best I can tell ( I don't use it) the Bondo product is a polyester resin not an epoxy. There are reasons some boat builders prefer epoxy over polyester but I doubt it makes a difference for what you are doing. More to the point is how will it look? The WEST is typically a clear to amber color similar to traditional varnishes. What does the bondo resin look like when it is cured?

They should be compatible if you clean the surface well before the second application. I know you can use WEST to bond to a polyester resin surface, so it should also work the other way.

You may also want to consider epoxies that are available in smaller kits. At this point you won't need anything like a full qt to finish the job. Sorry I can't offer suggestions, but check the boat supply sites- Jamestown distributor, Defender, West Marine, etc.

Good luck

 

[AllanD]

Not sure what your goals are either. If you want it to be clear then I would stay with epoxy. If you are most concerned with cost then contact Raka resins and see what they offer. If you want the clearest and thinnest self leveling epoxy, I like MAS. It's premium stuff though and not the cheapest. No blush either.

 

[marinosr]

This blog reports that Bondo is unsuitable for woodworking uses, due to the fact that it is rigid and will fall apart as wood shrinks and swells. Bondo is also truly nasty stuff to work with... you need a VOC respirator, which may negate cost savings if you don't own one.

 

[Bill Clemmons]

I'm sure there will be other answers but here's my quick take-
A Qt of anything will be 57.75 cu in. The gap you are trying to fill is around 40 cu in if the dimensions you give are close to correct.
So a qt of resin plus the hardener should be plenty to do the job unless something else is going on.
Did it leak out the other side?

I'm w/ smallboat on this one. Where did all that material go? That's 3 pints of material in a much smaller cavity.

 

[Jeff]

This is my first attempt at epoxy filling. I purchased a quart/pint of west system 105/206 and it didn't go near as far as I "wood" have hoped.

West system epoxy is one of the best available so you've got quality for your bucks! I'm curious. How far did you expect that "quart/pint" to go towards filling the void area? Did you also buy the metering pumps for accurately dispensing each component in the correct ratio for mixing or did you "eyeball" it when mixing? I too have the quart/pint of 105 resin and 206 hardener with the metering pumps and I don't understand how all of your epoxy just disappeared.

"Bondo" is not an epoxy, it can have the consistency of putty so it'll fill large voids quickly, and it's meant to be painted. It's simply crude and ugly so don't go there with your walnut slab!

http://salvagedinspirations.com/furniture-repair-bondo-vs-wood-filler/

 

[FredP]

I would mix the epoxy with some walnut saw dust to form a paste. fill the void with the paste and level after it cures.

 

[gritz]

Wood seasonally moves.
Bondo doesn't move.
Expect cracks around the bondo.

 

[ste6168]

I think many of you are thinking the Bondo that is typically used for auto-body repair (white/pink stuff once hardener is added). In this case, I think he is talking about a different product, made by the Bondo company, fiberglass resin.

I have no experience with either, so unfortunately I cant help, but just wanted to point that out.

 

[Jeff]

I have no experience with either, so unfortunately I cant help, but just wanted to point that out.

Thanks Mike. Is this the Bondo product that you were suggesting?

http://bondo.com/bondo-wood-filler-20082.html

 

[ste6168]

Thanks Mike. Is this the Bondo product that you were suggesting?

http://bondo.com/bondo-wood-filler-20082.html

This is what I believe the OP may be referring too.

http://bondo.com/products/fiberglass/bondo-fiberglass-resin-20122.html

 

[danmart77]

3490 Oleander Ave., Ft. Pierce, Florida 34982

Monday - Friday 8:00 AM to 5:00 PM (EST)
PH. 772.489.4070
fax 772.461.2070


The above address is for RAKA epoxy and supplies. I use them now instead of West for cost purposes and advice. Lots of good suppliers out there but I like RAKA for their epoxy thickening supplies.

I use a slow cure but I don't want it to run. RAKA sells a SILICA powder that you just mix in with the epoxy till you get the viscosity you want for the job. Sometimes I make it thick like butter other times a bit thinner. The silicone does not degrade the tack.

For a first timer I would encourage you to use a slow cure. Give yourself some working time you won't regret it.

good luck

 

[Jeff]

Different products for sure! I wouldn't use either one for a repair like the OP is attempting.

 

[smallboat]

Dan- did you mean to say silica rather than silicone?

I'll need to check out Raka for thickeners

Also, FWIW I was referring to the Bondo fiberglass resin product in my initial reply. I checked the MSDS to be sure that it was in fact a polyester resin not an epoxy.

 

[JimD]

For a clear finish situation I would definitely use the epoxy. They sell glass adders to increase the consistency and it would also tend to reduce the resin requirement. I fill little things with 5 minute epoxy from Harbor Freight. Sometimes I mix in sawdust.

For painted situations, I use good old auto body bondo. They sell a very similar, possibly the exact same, stuff for woodworking applications. I am not sure anything is different except the color. I used it to fill a bowed ceiling of a porch once. I used 1/4 waferboard, kerfed, to form the curved ceiling and needed to fill the voids. The bondo held up through multiple Pittsburgh winters. None of it came out or lifted in any way. There is another application in the room I am in right now. The puppies chewed away part of the window stool. I filled in the missing material with bondo, sanded to shape, and painted. Fix is not visible. That was much more recent but I am confident it will hold up. Cheap, easy to shape, works fine. I'm sure there are situations where they would move differently enough for the joint between the materials to fail but it hasn't happened to me. But I think it is better used where it will be painted and not show in the finished piece.

 

[Phil S]

I have used both polyester and epoxy resins. Epoxy is much stronger and has better bonding capability. I have used epoxy over polyester resins, but would not put polyester over epoxy - I suspect it would fail quickly

 

[danmart77]

Dan- did you mean to say silica rather than silicone?

I'll need to check out Raka for thickeners

Also, FWIW I was referring to the Bondo fiberglass resin product in my initial reply. I checked the MSDS to be sure that it was in fact a polyester resin not an epoxy.

I did mean to say Silica. I've got to cut back on my George Dickel before supper. Thanks.

The white Silica fluff comes in a bag. Its light as a feather and you just mix it in with the 2 part hardener and resin. Same old stuff really just a convenient way to thicken up your mix.

I started using it for laminated ribs for small boat construction. Its very nice in the glue up phase to minimize the slop and drip all over the place. It holds the glue in place as you "butter" the wood instead of brushing a wet coat on.

​

 

[cornbread]

Wow good information, thanks. For the bondo option I was looking at the polyester fiberglass resin, but after reading the responses I got some more 105/206 epoxy/hardener. My cube neighbor builds his own boats, kayaks (apparently is pretty darn good too) and was very familiar with the product and lent me his pumps.
First quart disappeared so quickly due to apparent knots being bigger internally than they appeared and several cracks literally drank the epoxy, the heart pine I epoxyed (which did turn out great) was hard to come by so I had to use pieces with a lot of cracks.

I did learn one lesson the hard way. A very hard way. I poured in too thick of an epoxy layer and the exothermic reaction heat cured the last layer too quickly. Hopefully since it's the underneath side it won't be noticeable but I fear I may have ruined this. Possibly an expensive lesson.

The top layer which I poured about 1" thick...I know, I suck resulted in bubbling, off gassing, too much heat, cracked the epoxy and left a lots of bubbles that I now can't remove